The investigation found thousands of marks on state test booklets changing answers from wrong to right, Baltimore and Maryland officials said. They reviewed hundreds of 2008 Maryland State Assessment booklets at George Washington Elementary School in southwest Baltimore for eighteen months.

Evidence of deception is clear, said Baltimore Schools CEO Andres Alonso, and the principal should be held responsible. The investigation did not reveal who actually altered the tests. Alonso told the Baltimore Sun that no staff member acknowledged taking part in or witnessing any cheating, and the principal did not provide an explanation.

State education officials believe it was a school-wide, orchestrated efforts to alter the test answers, a report said. They think the cheating happened across all grade levels and that it happened after the students finished taking the tests.

Alonso said what's more troubling is that the students' tests probably didn't need to be changed. After the test tampering was discovered and state and city monitors swooped in last year, the students performed well enough to meet federally mandated standards, according to the Sun.

In 2007, the school received the National Blue Ribbon, an award for schools that have made extraordinary progress with children from low-income families or maintained excellence for years. Nine out of 10 children at the school are poor. Test scores have been a source of pride for the city.

According to the Sun, when principal Susan Burgess arrived at the school in 2003, 32 percent of third-graders passed the state reading test. By July of 2007, 100 percent of students in some grades were passing the test and almost half had advanced scores.

Burgess's state teaching license was revoked, and she has retired.

Pressure of the principal and teachers to improve test scores is intense in most school districts, but state schools Superintendent Nancy Grasmick says cheating of this magnitude is relatively rare.